Ability to estimate the speed of a communication system terminal, such as a user terminal, is needed in increasing the capacity of a wireless system through improving the performance of a handover process, power control and/or channel assignment. For example, it is beneficial to choose for a high-speed user terminal a macro-cell instead of a micro-cell so as to reduce the number of handovers. Moreover, with the knowledge of the user terminal speed, the power control could be optimised, for example by choosing the averaging period of a power control algorithm according to the speed. Briefly, reliable estimates of the speed or, equivalently, the perceived channel Doppler spread, are of great importance in wireless systems.
A prior art method for estimating the speed is based on an average received power crossing rate. The algorithm is based on the comparison of signal level values and their averaged values. The algorithm calculates the rate with which a signal level crosses the averaged signal level due to fast fading. The crossing rate is proportional to the mobile speed.
Several problems arise from the prior art method. Firstly, the method is not suitable to be used with frequency hopping, since different frequencies have different fading characteristics. Secondly, the method fails to provide correct estimates when the speed is too high. This is due to the use of power crossing rate: when the power crossing rate exceeds the used sampling rate, the estimated speed values do not follow actual speeds anymore.